- Author: Therese Kapaun
Annual disease testing for Citrus tristeza virus (CTV) is nearly complete at LREC. Each year we test all field trees for presence of the virus using the Direct Tissue Blot Immunoassay method, which is a form of ELISA. This year we have more than 11,000 trees to test. CTV is found in the phloem tissues of citrus plants, and virus titer is typically highest during April in the San Joaquin Valley.
Field technicians Cody McCarter and Jessica Seymore work as a team to collect the tissue, which can be in the form of young flushing stalks or leaf petioles. The stalks or leaves are taken from the tree and the ends snipped with a cigar cutter for a smooth cut that is pressed onto a nitrocellulose membrane. The leaf material is then discarded, as the blots made onto the membrane contain enough phloem to reveal presence of the virus. Membranes are processed in-house in a laboratory, and results are obtained within four hours. Trees that are found to be infected are removed in order to protect research plots and foundation trees from infection.